Capacitors are widely used in consumer and commercial applications. As is well known to those having skill in the art, a capacitor generally includes spaced apart electrodes with a dielectric layer therebetween.
As the integration density of electronic devices continues to increase, it may become desirable to provide capacitors that have increasingly larger capacitance-per-unit-area of an integrated circuit substrate in which the capacitor is used and/or of a printed circuit board or other higher level package in which the capacitor is used. One way to increase the capacitance-per-unit-area is to increase the dielectric constant of the dielectric material.
In order to increase the dielectric constant of the dielectric material, perovskite dielectrics have been widely investigated and used. As is well known to those having skill in the art, perovskite dielectrics comprise a class of high permittivity ceramic dielectrics having a perovskite crystal structure and include dielectric oxides, such as lead zirconate titanate (PZT) and lead lanthanum zirconate titanate (PLZT). These dielectrics may be formed into very thin flexible robust layers with very high dielectric constants. As used herein, the term “perovskite dielectric layer” means a layer that includes one or more perovskite dielectrics, and may also include additional non-perovskite dielectric materials.
As is well known to those having skill in the art, a perovskite dielectric layer may be annealed at a high temperature, generally higher than about 500° C. and often at about 750° C. However, if an excessive oxygen partial pressure, such as an oxygen partial pressure that is greater than about 10−10 Torr, is present during the anneal, the beneficial effects of the anneal may be reduced and/or the anneal may cause other deleterious effects on the perovskite dielectric layer and/or other layers of the capacitor, integrated circuit or higher level package. Perovskite dielectric layers also may be used in many other applications, such as a gate insulating layer of a field effect transistor or an interlayer dielectric layer of an integrated circuit. The above-described deleterious effects also may take place during annealing in these other applications.
In view of the above, it is known to provide low oxygen partial pressures during annealing of a perovskite dielectric layer by vacuum annealing in an ultra-low pressure (ultra-high vacuum) environment, to obtain an oxygen partial pressure in the range of, for example, 10−10 Torr. Unfortunately, this high vacuum annealing may be difficult and/or expensive to maintain. It is also known to provide atmospheric or sub-atmospheric pressure annealing in an ultra-pure gas mixture having an extremely low oxygen partial pressure in the range of, for example, 10−10 Torr. For example, ultra-high purity gas mixtures between CO and CO2 and/or between H2 and H2O may provide sufficiently low oxygen partial pressure. Unfortunately, significant effort and/or expense may be needed to supply and maintain these ultra-high purity gases.